1. Field of the Invention
The present invention relates to a method for fabricating a magnetic head that includes the steps of growing films for a magnetic head which includes at least one of a magnetoresistive head and a thin-film head in a two-dimensional arrangement on a wafer, cutting out of the wafer a block in which a plurality of magnetic heads are arranged in a straight line, machining the element height of the magnetoresistive heads (height of the magnetoresistive head part) or the gap depth of the thin-film heads in units of blocks to a required value, and fabricating individual magnetic heads by dividing the blocks after the above process.
2. Description of Related Art
A known means to provide a reproducing head for high density is that of a magnetoresistive head which uses a magnetoresistive element, the electrical resistance of which changes in response to the strength of a magnetic field. This head is known as a magnetoresistive head (MR head), there being AMR (anisotropic magnetoresistive) heads which make use of the anisotropic magnetoresistive effect, and GMR (giant magnetoresistive) heads which make use of the giant magnetoresistive effect.
An AMR head comprises a soft adjacent layer made of a magnetized magnetic material such as NiFeCr (Nickel-Iron-Chrome), a non-magnetic center Ta (tantalum) layer, a magnetoresistive (MR) layer made of a material such as NiFe (ferrite), a BCS (boundary control stabilization) layer which is substantially magnetized and made of FeMn (Iron-manganese), that is an antiferromagnetic material, and a pair of conductive layers for the purpose of sense current supply which are arranged in parallel on the BCS layer with a spacing that corresponds to the recording track width, these layers being laminated in this sequence to fabricate a magnetoresistive effect element, a magnetic bias being applied to the magnetoresistive layer by means of the BCS layer in the width direction of the recording tracks, with a magnetic bias being applied to the magnetoresistive layer by means of the soft adjacent layer in the direction perpendicular to the BCS layer magnetic bias.
In a GMR head, by making use of the giant magnetoresistive effect, it is possible to achieve a significantly higher density than with an AMR head. The magnetoresistive element part of a GMR head also has a laminated structure in which a plurality of magnetic layers are laminated with an intervening non-magnetic layer, a pair of conductive layers for the purpose of sense current supply which are arrangement in parallel with a spacing that corresponds to the recording track width being mounting to the magnetoresistive element part.
The above-noted magnetoresistive head is capable of only reproducing, and cannot be used for recording. For this reason, it is usually used in combination with a thin-film head which performs recording, forming a compound magnetic head.
FIG. 1 is a drawing which shows the main part of a compound magnetic head, and FIG. 2 is a plan view which shows the magnetoresistive element part and conductive layer in FIG. 1.
In the above-noted drawings, the reference numeral 10 denotes a track on a magnetic recording medium, 20 is a recording head section formed by a thin-film head which performs recording of information onto the magnetic recording medium, and 30 is a reproducing section which is formed by a magnetoresistive head which performs reproduction of information. The recording head section 20 comprises a lower magnetic pole 21 which is made of, for example, NiFe, an upper magnetic pole 22 which is opposed to the lower magnetic pole 21 and which is made of, for example, NiFe, and a coil 23 which excites these magnetic poles 21 and 22, and which causes the recording of information onto the track 10 of the magnetic recording medium. In the space surrounding the coil 23, a non-magnetic insulating layer 24, made of Al.sub.2 O.sub.3 or the like, is provided so as not to leave any space therebetween.
The reproducing head 30 is formed by an AMR head, a GMR head or the like, and on the magnetoresistive element part 30A thereof, a pair of conducting layers 31 for the purpose of supplying a sense current to the magnetoresistive element part 30A, with a spacing that corresponds to the recording track width.
The laminated condition of the recording head section 20 and the reproducing head section 30 will be described with reference to FIG. 3. FIG. 3 is a cross-sectional view which shows the laminated structure of the region of the gap of the magnetic head as seen from the magnetic recording medium. In FIG. 3, the reference numeral 25 denotes a ceramic substrate, onto which a non-magnetic insulating layer 26 of Al.sub.2 O.sub.3 or the like, a lower shielding layer 27 of NiFe or the like, and a non-magnetic insulating layer 28 of Al.sub.2 O.sub.3 or the like are formed, in that sequence, the magnetoresistive element part 30A of the reproducing head 30 being formed on top of this non-magnetic insulating layer 28. If the magnetoresistive element part 30A of the reproducing head 30 were to be formed by an AMR head, a soft adjacent layer, a non-magnetic center layer made of Ta or the like, a magnetoresistive layer made of NiFe or the like, and a BCS layer made of FeMn or the like would be formed in that sequence on the non-magnetic insulating layer 28. On top of this magnetoresistive element part 30A is formed a pair of conductive layers 31 for the purpose of supplying a sense current to the magnetoresistive element part 30A, these layers having a spacing which corresponds to the recording track width.
Additionally, a non-magnetic insulating layer 32 is formed on the magnetoresistive element part 30A and the conductive layer 31, and on top of this is formed a recording head section 20. That is, the lower magnetic pole (lower shielding layer) 21 made of NiFe or the like, the coil 23 (not shown in FIG. 3), the non-magnetic insulating layer 24 made of Al.sub.2 O.sub.3 or the like, and the upper shielding layer 22 made of NiFe or the like are formed in this sequence. Then finally a protecting layer 33 made of Al.sub.2 O.sub.3 or the like is formed on the outside of the upper magnetic pole 22 for the purpose of covering the surface of the recording head section 20.
In fabricating a magnetic head having the structure noted above, the process comprises the steps of growing the films, onto a wafer, for many magnetic heads arranged in a two-dimensional arrangement, cutting out of the wafer a block in which a plurality of magnetic heads is arranged in a straight line, machining the element height of the magnetoresistive heads or the gap depth of the thin-film heads in units of blocks to a required value, and fabricating individual magnetic heads by dividing the blocks after the above process.
In doing this, it is necessary that the element height of a magnetoresistive head (the up/down direction width of the magnetoresistive element part 30A in FIG. 3) or the gap depth of a thin-film head (the up/down direction width of the gap part in FIG. 3) be machined by lapping or the like to a precise value, because of the critical effect this has on the characteristics of a magnetic head. This machining is performed in the above-noted steps. A known method of machining the element height of a magnetoresistive head or the gap depth of a thin-film head to be machined to a given value as a block by lapping or the like, is to form a machining reference resistance pattern which decreases as the machining proceeds on the block at the wafer process, and to stop the machining at the point in time at which the resistance value of the machining reference resistance pattern reaches a prescribed value.
However, there is a great deal of variance in the film thickness of the machining reference resistance pattern and the resistivity thereof. With regard to the film thickness in particular, this is not uniform even within one and the same wafer. For this reason, there is the problem that even if the resistance value of the machining reference resistance pattern reaches the prescribed value (target value), it is not possible to machine the element thickness of the magnetoresistive head or the gap depth of a thin-film head to a given value, and in the method of fabricating a magnetic head having a structure as noted above, making it impossible to achieve precise machining of the element height in a magnetoresistive head or the gap depth in a thin-film head.
As a solution to the above-noted problem, it is possible to envision the setting of a target resistance value for each block individually (the block being the unit for machining, also known as the workpiece). This is not realistic, however, and does not allow automation of the process. There is also the method of not measuring the resistance value, but rather directly measuring the shape of the pattern, and stopping the machining at the point at which a dimension thereof reaching a prescribed value. However, in that fabrication method, it is necessary to stop the process a number of times as machining proceeds for the purpose of measuring the shape of the pattern, this process being accompanied by the risk of removing excessive material, not only making it difficult to actually achieve highly precise machining, but also preventing automation of the process.